Spatial light modulators (SLMs) are commonly used for image display applications. In general, an SLM is an array of pixels, which are individually addressable, usually with electronic signals. Many SLMs are binary, having an addressing scheme that switches the pixels to either to an "on" or an "off" state to form the image. Various modulation and integration schemes are used to provide greyscale images.
One type of SLM is a digital micro-mirror device (DMD), sometimes referred to as a deformable mirror device. The DMD has an array of hundreds or thousands of tiny tilting mirrors, each of which represents one pixel. To permit the mirrors to tilt, each is attached to one or more hinges mounted on support posts, and spaced by means of an air gap over underlying control circuitry. The control circuitry provides electrostatic forces, which cause each mirror to selectively tilt. For display applications, image data is loaded to the DMD, and in accordance with the data, light is selectively reflected or not reflected from each mirror to an image plane.
An advantage of SLMs is that they can be made very small, and are far less bulky than older types of display devices, such as those that use a cathode ray tube. This permits the development of smaller display systems, with the image being projected from the SLM to a screen of the desired size.